In many computer systems, system power specification is based upon analytical models. Such analytical models make certain assumptions about the power consumption by various components in a system.
FIG. 1 is a block diagram illustrating a prior art power distribution system. The system 100 includes a power supply 115, which receives power input 110. The power input 110 may be a DC power source (e.g., power from a battery) or an AC power source (e.g., power from a wall outlet). The power supply 115 may distribute power to multiple components such as, for example, central processing unit (CPU) or processor 130, memory 140, chipset 150, adapters 160, I/O devices 170, etc. The power supply 115 may first distribute power to a voltage regulator 120 which then control power distributed to a component (e.g., processor 130). The rating or capacity of the power supply 115 may depend on the power consumption rating of all of the components and thus of the system 100. When the power consumption of the system 100 exceeds the rating of the power supply 115, the power supply 115 may shut down.
It may be difficult to predict the power consumption rating of each of the components in the system to accommodate all possible scenarios. New usage models, applications and data patterns make the prediction even more difficult. When a new usage model makes the components demand more power than what the power supply can provide, the power supply 115 and accordingly the system 100 may fail. Other factors may also be considered to predict the power consumption rating of a component. These factors may include, for example, variation in power consumption of a component manufactured by different vendors. The sum of the power consumption rating of all of the components may also be used to determine system power specification. The system power specification may then be compensated upward to give some safeguard. This compensated system power specification may then be used to select the appropriate rating for the power supply 115. For example, the power supply 115 may have a maximum rating that is a percentage (e.g., 20 percent) higher than the system power specification. Thus, the rating of the power supply 115 may be larger and more expensive than necessary.
Facility managers typically rely on the rating of the power supply 115 to determine the amount of power and cooling to be allocated to the system 100. For example, computer systems such as the system 100 are typically installed on in racks. The racks have limited power and cooling capability. The facility managers may use the rating of the power supply (normally specified on a name plate placed on the back of a system) to determine the number of systems that can go on a rack. With the system power specification (and thus the rating of the power supply) growing every generation, the number of systems that can be supported by a rack decreases. As a result, there may be empty spaces on the rack causing wastage of expensive data center space and infrastructure.